Gpu-Based Parallel Computations of the Hydrological Regime in the Kiliya Delta of the Danube River

A mathematical model of the hydraulic regime of the Danube Kiliya Delta based on the two-dimensional parallel shallow-water hydrodynamic model COASTOX-UN is described. This model uses unstructured computational grids with triangular cells. The parallelization algorithm for solving the model equations on graphics processing units (GPUs) is presented using the FCT scheme of the model as an example. The high computational efficiency on GPUs is demonstrated: the modeling speed increases by more than 100 times compared to single-core computation and about five times compared to the parallel MPI version on a multi-core workstation. The use of GPUs makes it possible to calculate hydrodynamic processes in a large part of the delta on a detailed grid of high dimensionality. Verification of the model with hydrological station data from the Danube Hydrometeorological Observatory confirms its accuracy in reproducing water level and discharge dynamics in the delta branches. This is supported by a high correlation between calculations and field measurements as well as a high index of agreement. A prediction based on the modified delta model showed that the planned reconstruction of the Danube — Black Sea Deep Water Navigation Route (DWNR) will have a negligible impact on the hydraulic regime of the delta. The deviations of the water discharge do not exceed 3,5 % of the current runoff distribution, and the lowering of the water level in the branches of the delta does not exceed 6 cm on average in the section from Kiliya city to the sea.